Regarding a fuser unit that is used in an image forming apparatus of an electrophotographic method, it is known that a fuser unit of which a heat source (heat generator) such as halogen lamp, a thermistor (temperature detecting member) and the like are arranged at the inside of a belt (heating belt) made of a heat-resistant film. In the fuser unit, the heat source is controlled based on temperatures detected by the temperature detection unit, so that a fixing temperature and the like are controlled.